GB2357317A

GB2357317A - Controlling the actuating fluid pressure of an i.c. engine compression release brake

Info

Publication number: GB2357317A
Application number: GB0030454A
Authority: GB
Inventors: Joshua C Ruedin; Scott A Leman; Steven J Funke; Matthew G Mickiewicz
Original assignee: Caterpillar Inc
Current assignee: Caterpillar Inc
Priority date: 1999-12-16
Filing date: 2000-12-14
Publication date: 2001-06-20
Anticipated expiration: 2020-12-14
Also published as: GB0030454D0; US6205975B1; GB2357317B; DE10060647A1; CA2326867A1

Abstract

The present invention provides a method and apparatus for controlling an actuation of a compression release brake associated with an i.c. engine having a cylinder with an associated exhaust valve 42 . The engine includes a fluid circuit for delivering an exhaust valve actuating fluid to the compression brake. For example, the fluid may act to urge a piston 72 against a contact rod 82 carried by the exhaust valve rocker arm 20. The method includes the steps of establishing a desired timing of an actuation of the brake 64, determining an air pressure of the engine, and determining a desired fluid pressure in response to the timing and the air pressure. The invention addresses the problem that excessive actuating fluid pressure may cause the exhaust valve to overshoot and interfere with piston, while insufficient fluid pressure may not be able to open the exhaust valve. The engine air pressure may be sensed as intake manifold pressure, boost pressure or in-cylinder pressure. The temperature of the actuating fluid may be sensed so that the control system can account for changes in the viscosity of the fluid. A desired braking torque may be determined from desired and actual engine speeds.

Description

1 2357317 1 Method and Apparatus of Controlling the Actuation of 2 a

Compression Brake 3 4

6 Technical Field

7 The present invention relates generally to 8 engine compression release brakes, and more 9 particularly, to a method and apparatus of controlling the actuation of a compression brake.

11 12 Background Art

13 Engine retarding devices of the compression 14 release type may be utilized in work machines such as on-highway trucks and the like. A compression 16 release brake assembly utilizes compression within 17 the truck's engine to assist the truck's main braking 18 system in order to slow the truck. In effect, such 19 compression release brake assemblies convert the truck's internal combustion engine into an air 2 1 compressor in order to develop retarding horsepower 2 which is utilized to assist in slowing the truck.

3 Compression release brake assemblies which 4 have previously been designed typically include a fluid system having a master cylinder having a piston 6 which is actuated by a cam lobe or push rod 7 associated with an exhaust valve, intake valve, or 8 fuel injector corresponding to a first engine 9 cylinder. Actuation of the piston associated with the master cylinder controls actuation of a piston 11 associated with a slave cylinder which selectively 12 opens and closes the exhaust vale of a second, 13 different engine cylinder near the end of the 14 compression stroke thereby causing the mechanical work performed during the compression stroke to be 16 dissipated and hence not "recovered" during the 17 subsequent power stroke.

18 In one embodiment of a hydraulically 19 actuated compression brake, controlling the pressure of the hydraulic fluid may be useful in achieving the 21 desired timing of the opening of the exhaust valve, 22 with the desired force. As the cylinder pressure 23 varies within a cylinder, the desired force for 24 opening the exhaust valve also varies. Excessive exhaust actuation speed, which may be caused by 26 excessive actuating fluid pressure, may cause a 27 reduction in the service life of the exhaust valve.

28 For example, if the actuating fluid pressure is too 29 high, the lift of the exhaust valve may potentially overshoot and interfere with the piston, thereby 31 potentially damaging the piston or valve. In 3 1 addition, the faster the exhaust valve closes, which 2 may be influenced by fluid pressure, the greater the 3 velocity at which the exhaust valve seats. If the 4 exhaust valve closes too rapidly, damage to the exhaust valve and/or the associated valve seat may 6 occur. An inadequate actuating fluid pressure may 7 result in the exhaust valve not being opened.

8 The present invention is directed to 9 overcoming one or more of the problems identified above.

11 12 Disclosure of the Invention

13 According to a first aspect of the present 14 invention there is provided a method of controlling the actuation of a compression brake in accordance

Claims

16 with Claim 1. According to a second aspect of the

17 present invention there is provided an apparatus 18 adapted to control an actuation of a compression 19 brake in accordance with Claim 16.

In one aspect of the present invention, a 21 method of controlling an actuation of a compression 22 brake associated with a combustion engine is 23 disclosed. The engine has a fluid circuit for 24 delivering a fluid to the compression brake. The engine also includes a cylinder having an associated 26 exhaust valve. The method includes the steps of 27 determining a desired timing of an actuation of the 28 brake, determining an air pressure of the engine, and 29 determining a desired fluid pressure in response to said timing and said air pressure.

4 1 In another aspect of the present invention, 2 an apparatus adapted to control an actuation of a 3 compression brake associated with a combustion engine 4 is disclosed. The engine includes a fluid circuit for delivering a fluid to the compression brake, the 6 fluid enabling the control of the compression brake.

7 The engine includes a cylinder having an associated 8 exhaust valve. The apparatus includes a speed sensor 9 adapted to sense an engine characteristic indicative of an engine speed and responsively generate a speed 11 signal, an air pressure sensor adapted to sense a 12 characteristic indicative of an engine air pressure 13 and responsively generate an air pressure signal, and 14 a controller adapted to receive the speed signal and the air pressure signal, establish a desired timing 16 of an actuation of said brake, determine an air 17 pressure of said engine in response to said air 18 pressure signal, and determine a desired fluid 19 pressure in response the air pressure.

21 Brief Description of the Drawings 22 FIG. 1 is an internal combustion engine 23 which incorporates the features of the present 24 invention therein; FIG. 2 is a schematic view of the internal 26 combustion engine of FIG. 1; 27 FIG. 3 is a cross sectional view of the 28 actuator assembly of the compression release brake 29 assembly of the internal combustion engine of FIG. 1, note that the solenoid-controlled hydraulic valve is 1 not shown in cross section for clarity of 2 description; 3 FIG. 4 is a side elevational view which 4 shows the actuator assembly of the compression release brake assembly of FIG. 3 being utilized in 6 the design of an overhead cam engine; 7 FIG. 5 illustrates a flow chart of one 8 embodiment of the present invention; 9 FIG. 6 illustrates one embodiment of a cylinder pressure map; and 11 FIG. 7 illustrates one embodiment of a 12 desired fluid pressure map.

13 14 Best Mode for Carrying Out the Invention The present invention provides a method and 16 apparatus of controlling the actuation of a 17 compression brake associated with a combustion 18 engine. FIGS. 1 and 2, illustrate one embodiment of 19 an internal combustion engine such as a diesel engine 10. The engine 10 is shown in the drawings, 21 and will be described herein, as a six-cylinder 22 diesel engine; however, it should be appreciated that 23 the engine 10 of the present of invention could be 24 embodied as any type of internal combustion engine with any number of cylinders.

26 The engine 10 includes an engine block and 27 head assembly 12 having a pair of rocker arm shafts 28 14, 16 secured thereto. The rocker arm shaft 14 has 29 a number of intake rocker arms 18 rotatably secured thereto, whereas the rocker arm shaft 16 has a number 31 of exhaust rocker arms 20 rotatably secured thereto.

6 1 Each of the intake rocker arms 18 has a roller 22 2 coupled thereto which is selectively contacted by a 3 number of cam lobes (not shown) associated with an 4 intake cam shaft 24. In particular, rotation of the intake cam shaft 24 causes the cam lobes associated 6 therewith to be selectively moved into and out of 7 contact with the rollers 22 of each of the intake 8 rocker arms 18. Contact with one of the intake 9 rocker arms 18 by the cam lobes causes the intake rocker arm 18 to pivot or otherwise rotate about the 11 rocker arm shaft 14 thereby causing a valve contact 12 rod 26 associated with the intake rocker arm 18 to 13 contact an upper portion of a valve stem 28 of an 14 intake valve 30. Such contact with the upper portion is of the valve stem 28 urges the intake valve 30 16 downwardly thereby opening the intake valve 30 so as 17 to allow air to flow into the associated engine 18 cylinder in a known manner.

19 Similarly, each of the exhaust rocker arms 20 has a roller 32 (see FIG. 4) coupled thereto which 21 is selectively contacted by a number of cam lobes 34 22 associated with an exhaust cam shaft 36. In 23 particular, rotation of the exhaust cam shaft 36 24 causes the cam lobes 34 to be selectively moved into and out of contact with the rollers 32 of each of the 26 exhaust rocker arms 20. Contact with one of the 27 exhaust rocker arms 20 by the cam lobes 34 causes the 28 exhaust rocker arm 20 to pivot or otherwise rotate 29 about the rocker arm shaft 16 thereby causing a valve contact rod 38 associated with the exhaust rocker arm 31 20 to contact an upper portion of a valve stem 40 of 7 1 an exhaust valve 42. Such contact with the upper 2 portion of the valve stem 40 urges the exhaust valve 3 42 downwardly thereby opening the exhaust valve 42 so 4 as to allow gas within the associated engine cylinder to flow from the cylinder.

6 The engine 10 also includes a 7 hydraulically-powered fuel injection system 44, as 8 illustrated in Fig. 2. The fuel injection system 44 9 includes a number of fuel injectors 46 which are provided to selectively inject fuel into an 11 associated engine cylinder. The hydraulically- 12 powered fuel injection system 44 of the present 13 invention may be provided as any known hydraulically 14 powered fuel injection system; however, one such hydraulically powered fuel injection system which is 16 particularly useful as the hydraulically-powered fuel 17 injection system 44 of the present invention is a 18 Hydraulic Electronic Unit Injection (HEUI) system 19 which is commercially available from Caterpillar, Incorporated of Peoria, Illinois.

21 The hydraulic pump 50 is generally driven 22 by the engine 10 and is provided to pump hydraulic 23 fluid from a reservoir or sump 52 to the fluid 24 manifold 48. Each of the fuel injectors 46 is fluidly coupled to the fluid manifold 48 such that 26 fluid pressure from the manifold 48 may be utilized 27 to generate a relatively high fuel pressure from the 28 fuel within the fuel injectors 46. In particular, 29 the engine 10 further includes a fuel system 54 which has a fuel pump 56 for pumping fuel to each of the 31 fuel injectors 46. The fuel within the fuel 8 1 injectors 46 is pressurized via a plunger assembly 2 (not shown) which is driven by the fluid pressure 3 from the fluid manifold 48.

4 Moreover, each of the fuel injectors 46 includes a high-speed, solenoid-actuated hydraulic 6 valve 58 which is electrically coupled to an engine 7 control module 60, or controller, via a wiring 8 harness 62. In such a manner, the engine control 9 module 60 may selectively generate injection pulses which are sent to the individual solenoid-actuated 11 hydraulic valves 58 so as to open the valve 58 12 thereby increasing the fluid pressure exerted on the 13 plunger assembly of the associated fuel injector 46 14 which in turn increases the fuel pressure within the injector 46. Such an increase in the fuel pressure 16 within the fuel injector 46 causes fuel to be 17 injected into the engine cylinder associated with the 18 particular fuel injector 46. It should be 19 appreciated that the engine control module 60 may operate the fuel injectors 46 in wide variety of 21 manners in order to generate injection sequences and 22 operation characteristics which fit the needs of a 23 given engine 10.

24 The engine 10 also includes a hydraulically-powered compression release brake 26 assembly 64. The compression release brake assembly 27 64 includes a number of actuator assemblies 66 (see 28 also FIG. 3) which are provided to selectively open 29 the exhaust valves 42 associated with the engine 10 when the engine 10 is being operated in a brake mode 31 of operation. Each of the actuator assemblies 66 9 1 includes a housing 68 having a fluid chamber 70 2 defined therein for housing a piston 72. Each of the 3 actuator assemblies 66 also includes a high-speed, 4 solenoid-actuated hydraulic valve 74. The solenoid s actuated hydraulic valves 74 are similar to the 6 solenoid-actuated hydraulic valves 58. For example, 7 one high-speed, solenoid-actuated hydraulic valve 8 which may be utilized as the solenoid-actuated 9 hydraulic valves 74 of the present invention are the solenoid-actuated hydraulic valves which are utilized 11 to actuate the fuel injectors of the abovenoted HEUI 12 fuel injection system. Such solenoid-actuated 13 hydraulic valves are likewise commercially available 14 from Caterpillar.

is The housing 68 of the actuator assembly 66 16 has a number of input fluid passages 76 and drain 17 fluid passages 78 defined therein. The solenoid 18 actuated hydraulic valve 74 selectively couples the 19 input fluid passages 76 to the fluid manifold 48. In particular, when the solenoid-actuated hydraulic 21 valve 74 is positioned in an open position, 22 pressurized hydraulic fluid is advanced from the 23 fluid manifold 48, into an input port associated with 24 the valve 74, out an output port associated with the valve 74, and into the input fluid passages 76 and 26 hence the fluid chamber 70. The presence of 27 pressurized hydraulic fluid in the fluid chamber 70 28 causes the piston 72 to be urged upwardly (as viewed 29 in FIG. 3) and into an extended position in which a contact side 80 of the piston 72 is urged into 31 contact with a portion of the exhaust rocker arm 20.

1 In particular, as shown in FIG. 4, a 2 contact rod 82 is secured to an extension member 84 3 of each of the exhaust rocker arms 20. When the 4 contact rod 82 is contacted by the piston 72, the contact rod 82 is urged upwardly (as viewed in FIG.

6 4) so as to urge the extension member 84 of the 7 exhaust rocker arm 84 upwardly. Movement of the 8 extension member 84 in an upward direction (as viewed 9 in FIGS. 3 and 4) causes the exhaust rocker arm 20 to pivot or otherwise rotate about the rocker arm shaft 11 16 thereby causing the valve contact rod 38 12 associated with the exhaust rocker arm 20 to contact 13 the upper portion of a valve stem 40 of the exhaust 14 valve 42. Such contact with the upper portion of the is valve stem 40 urges the exhaust valve 42 downwardly 16 thereby opening the exhaust valve 42 so as to allow 17 gas within the associated engine cylinder to flow 18 from the cylinder. The speed sensor 106 enables the 19 engine timing, e.g., piston position, to be monitored and determined.

21 It should be appreciated that operation of 22 the actuator assemblies 66 is under the control of 23 the engine control module 60. In particular, each of 24 the solenoid-actuated hydraulic valves 74 is coupled to the engine control module 60 via a wiring harness 26 86. In such a manner, the engine control module 60 27 may selectively generate pulses which are sent to the 28 individual solenoid-actuated hydraulic valves 74 so 29 as to open the valve 74 thereby causing pressurized hydraulic fluid to be advanced from the fluid 31 manifold 48 to a fluid side 88 of the piston 72 so as 1 to urge the piston 72 upwardly (as viewed in FIG. 3).

2 Such upward movement of the piston 72 causes rotation 3 of the exhaust rocker arm 20 and hence opening of the 4 exhaust valve 42 thereby allowing gas to be advanced out the associated engine cylinder. Once the exhaust 6 valve has been opened for a period of time, the 7 engine control module 60 ceases to generate a pulse 8 on the wiring harness 86 thereby causing the 9 particular exhaust valve 42 to be closed.

As shown in FIG. 4, there is a gap of a 11 predetermined distance between the contact side 80 of 12 the piston 72 and the lower surface of the contact 13 rod 82 in order to prevent the exhaust valve 84 from 14 being inadvertently held open during operation of the engine 10 which could potentially reduce the useful 16 life of the exhaust valve 42.

17 The engine 10 also includes a speed sensor 18 106. The speed sensor 106 is adapted to sense a 19 characteristic of the engine 10 that is indicative of engine speed and responsively deliver a speed signal 21 to the controller 60. For example, in operation, the 22 crankshaft (not shown) of the engine 10 rotates when 23 the engine 10 is being operated. The rotation of the 24 crankshaft results in the piston(s) of the engine moving between a top dead center position and a 26 bottom dead center position. In one embodiment, the 27 speed sensor 106 monitors the rotational position of 28 the crankshaft and sends an associated signal to the 29 controller 60. A particular piston position may be determined by correlating a piston position with the 31 sensed crank angle position. Therefore, by 12 1 monitoring the crank angle position, the piston 2 position may be determined. The speed sensor 106 may 3 be a crankshaft sensor that is disposed adjacent to 4 the crankshaft flywheel (not shown). The sensor monitors the rotational position of the engine 6 crankshaft and responsively produces a crankshaft 7 pulsetrain. The crankshaft sensor may be an optical 8 or magnetic type sensor.

9 It should also be appreciated that the engine control module 60 controls operation of the 11 fuel injectors 46 and the brake actuator assemblies 12 66 in order to control output from the engine 10. In 13 particular, the engine 10 is operable in either a 14 drive mode of operation or a brake mode of operation.

is When the engine 10 is being operated in its drive 16 mode of operation, the engine control module 60 17 controls the fuel injectors 46 such that fuel is 18 injected into the engine cylinders so as to cause 19 combustion within the engine cylinders in order to produce positive mechanical output from the engine 10 21 thereby driving the drive train (not shown) of a work 22 machine such as an on-highway truck. It should be 23 noted that when the engine 10 is being operated in 24 its drive mode of operation, the intake valves 30 and the exhaust valves 42 are operated in a known manner 26 (i.e. selectively opened and closed) by the camshafts 27 24, 36, respectively, such that the intake valves 30 28 are opened during the intake stroke of the engine 10, 29 whereas the exhaust valves 42 are opened during the exhaust stroke of the engine 10.

13 1 Moreover, when the engine 10 is operated in 2 its drive mode of operation, the compression release 3 brake assembly 64 is idled. In particular, during 4 operation of the engine 10 in its drive mode of operation, the engine control module does not open 6 any of the solenoid-controlled hydraulic valves 74 7 associated with actuator assemblies 66 thereby 8 isolating the fluid chamber 70 from the fluid 9 manifold 48. Such isolation of the fluid chamber 70 from the fluid manifold 48 positions the piston 72 in 11 its retracted position thereby preventing it from 12 contacting the contact rod 82.

13 Conversely, when the engine 10 is being 14 operated in its brake mode of operation, the engine control module 60 controls the actuator assemblies 66 16 of the compression release brake assembly 64 such 17 that the exhaust valves 42 are selectively opened in 18 order to release compressed gas within the engine 19 cylinders. In particular, the engine control module 60 may generate an output pulse which opens the 21 solenoid-controlled valve 74 of a particular actuator 22 assembly 66 thereby causing the piston 72 to urge the 23 contact rod 82 upwardly which in turn opens the 24 exhaust valve 42 in the manner described above.

Moreover, when the engine 10 is operated in 26 its brake mode of operation, the fuel injection 27 assembly 44 is idled. In particular, during 28 operation of the engine 10 in its brake mode of 29 operation, the engine control module 60 does not open any of the solenoid-controlled hydraulic valves 58 31 associated with the fuel injectors 46 thereby 14 1 preventing fuel from being injected into the 2 corresponding engine cylinders.

3 In one embodiment, the controller 60 4 receives one or more sensor inputs and responsively controls an actuation of the compression brake. In 6 one embodiment, the controller 60 establishes a 7 desired timing of the brake actuation, determines an 8 air pressure of the engine, determining a desired 9 fluid pressure in response to the desired timing and the desired fluid pressure, and controls the brake 11 actuation in response to the desired fluid pressure.

12 Fig. 5 illustrates one embodiment of a 13 method of the present invention. In a first control 14 block 502, a desired timing of the brake actuation is is established. Establishing the desired brake 16 actuation timing may be implementation dependent. In 17 one embodiment, the timing may be dynamically 18 determined in response to a desired engine speed and 19 an actual engine speed. For example, a desired braking torque may be dynamically determined in 21 response to the desired and actual engine speeds. A 22 timing map may be utilized to dynamically determine a 23 desired start of brake actuation timing in response 24 to the desired braking torque and actual engine speed. In an alternative embodiment the desired 26 timing may be a fixed value. For example, 27 establishing the desired timing may include accessing 28 a predetermined desired timing from memory within the 29 controller 60.

In a second control block 504, the air 31 pressure of the engine is determined. In the 1 preferred embodiment, the air pressure to be 2 determined is the boost pressure of the engine. An 3 intake manifold pressure sensor 108 may be used to 4 sense a parameter indicative of the boost pressure of the engine and responsively deliver a boost pressure 6 signal to the controller 60. The intake manifold 7 pressure sensor 108 may be a pressure transducer of 8 any suitable commercially available type connected to 9 and disposed into the intake manifold (not shown).

In an alternative embodiment, to be discussed below, 11 the air pressure to be determined may be the cylinder 12 pressure within a respective cylinder.

13 In a third control block 506 a desired 14 fluid pressure may be determined in response to the is desired timing of the brake actuation and the air 16 pressure. e.g., boost pressure. In one embodiment, a 17 cylinder pressure is determined in response to the 18 desired actuation timing and the boost pressure.

19 Fig. 6 illustrates a map of cylinder pressure correlated with piston position. The piston position 21 illustrated in Fig. 6 may be indicative of the actual 22 engine speed, or a representative illustration of the 23 rotation of the piston. As discussed, piston 24 position may be determined from a sensed crank angle position. Multiple pressure curves may be utilized 26 in the map, representing different boost pressures.

27 For example, a first cylinder pressure curve 602 28 correlates cylinder pressure with piston position for 29 a first sensed boost pressure, e.g., one atmospheric pressure. A second cylinder pressure curve 604 31 correlates cylinder pressure with piston position for 16 1 a second sensed boost pressure, e.g., two atmospheric 2 pressures. In one embodiment, the cylinder pressure 3 curves may be predetermined through empirical 4 analysis of engine performance. The number of cylinder pressure curves utilized may be 6 implementation dependent.

7 During operation, the boost pressure may be 8 sensed. The cylinder pressure may then be determined 9 in response to the boost pressure and the desired brake actuation timing. For example, in one 11 embodiment, the pressure curve having an associated 12 boost pressure closest to the sensed boost pressure 13 may be utilized. For example, when the sensed boost 14 pressure is closest to one atmosphere, the first pressure curve 602 may be utilized. Then, if the 16 desired brake actuation timing, illustrated as 17 desired timing 606, is twenty degrees before top dead 18 center, the pressure within the cylinder may be 19 determined to be a first cylinder pressure 608. That is, the first cylinder pressure 608 is indicative of 21 the force needed to be overcome to achieve the 22 desired actuation timing. The value of twenty 23 degrees before top dead center is used here for 24 exemplary purposes only.

In an alternative embodiment, if a sensed 26 boost pressure falls between the boost pressure 27 associated with the first pressure curve 602 and the 28 boost pressure associated with the second pressure 29 curve 604, then interpolation techniques may be used to determine the appropriate cylinder pressure.

17 1 once a cylinder pressure has been 2 determined, another map may be utilized which 3 correlates cylinder pressure with desired fluid 4 pressure. The desired fluid pressure is the pressure of the fluid needed to achieve the desired opening of 6 the exhaust valve 42. Therefore, a desired fluid 7 pressure map may be determined through empirical 8 analysis to determine a desired fluid pressure that 9 will enable a desired opening of the exhaust valve based upon the cylinder pressure. Fig. 7 illustrates 11 a map correlating cylinder pressure with desired 12 fluid pressure. The map may vary based upon desired 13 valve opening, or valve lift. Fig. 7 is for 14 exemplary purposes only. The actual values of the map are implementation and engine dependent, and may 16 be empirically determined.

17 In an alternative embodiment, a single map 18 may be used that correlates desired fluid pressure 19 with desired brake actuation timing and boost pressure. The desired pressure values may be 21 empirically determined, and then downloaded and 22 stored in the controller 60 for use during the 23 operation of the engine.

24 In a fourth control block 508, the actuation of the compression brake is controlled in 26 response to the desired fluid pressure. As 27 illustrated in Fig. 2, the engine 10 may include an 28 Injector Actuation Pressure Control Valve (IAPCV) 29 104. In the preferred embodiment, the IAPCV 104 and the hydraulic pump 50 enable the controller 60 to 31 maintain the desired pressure of the actuating fluid.

18 1 For example, in one embodiment, a pressure sensor 102 2 senses the actual pressure of the actuating fluid and 3 responsively delivers a fluid pressure signal to the 4 controller 60. The controller 60 compares the actual fluid pressure and the desired fluid pressure and 6 responsively delivers a command signal to the IAPCV 7 104 to achieve the desired fluid pressure. In one 8 embodiment, the pump 50 is a variable displacement 9 pump, and may be used to control the pressure of the actuating fluid. The controller 60 compares the 11 actual fluid pressure and the desired fluid pressure 12 and responsively delivers a command signal to the 13 variable displacement pump 50 to achieve the desired 14 fluid pressure.

is In an alternative embodiment of the present 16 invention, a desired brake actuation timing and an 17 engine air pressure are determined. The engine air 18 pressure determined is the actual cylinder pressure.

19 A cylinder pressure sensor (not shown) may be used to sense the pressure within a cylinder and deliver a 21 cylinder pressure signal to the controller 60. The 22 cylinder pressure sensor may be disposed on the top 23 of the piston. For example, the cylinder pressure 24 sensor may be of a piezoelectric construction. Then, a cylinder pressure map, as illustrated in Fig. 7 may 26 be used to correlate a desired fluid pressure with 27 the cylinder pressure. The actuation of the brake 28 may then be controlled in response to the desired 29 fluid pressure.

In one embodiment, a temperature sensor 31 (not shown) may be used to sense the temperature of 19 1 the actuating fluid and deliver a corresponding 2 signal to the controller 60. The temperature may be 3 used to account for a viscosity of the actuating 4 fluid. That is, the desired fluid pressure may vary as a result of changes in the viscosity of the 6 actuating fluid. Therefore, the desired fluid 7 pressure may be determined in response to the desired 8 timing of the brake actuation, the boost pressure, 9 and the fluid temperature. The impact of the fluid temperature on desired fluid pressure may be 11 empirically determined and accounted for in the 12 associated desired pressure maps.

13 While the invention has been illustrated 14 and described in detail in the drawings and foregoing description, such illustration and description is to 16 be considered as exemplary and not restrictive in 17 character, it being understood that only the 18 preferred embodiments have been shown and described 19 and that all changes and modifications that come within the spirit of the invention are desired to be 21 protected.

22 23 Industrial Applicabilit 24 In operation, the engine 10 of the present invention may be utilized to provide motive power to 26 a work machine such as an on-highway truck or an off 27 highway work machine. The engine 10 is operated in 28 its drive mode of operation in order to advance the 29 truck. When the engine 10 is operated in its drive mode of operation, the engine control module 60 31 operates the fuel injectors 46 such that fuel is 1 injected into the engine cylinders so as to cause 2 combustion within the engine cylinders.

3 when the engine 10 is operated in its drive 4 mode of operation, the compression release brake assembly 64 is idled. In particular, during 6 operation of the engine 10 in its drive mode of 7 operation, the engine control module 60 does not open 8 any of the solenoid-controlled hydraulic valves 74 9 associated with actuator assemblies 66 thereby isolating the fluid chamber 70 from the fluid 11 manifold 48. Such isolation of the fluid chamber 70 12 from the fluid manifold 48 positions the piston 72 in 13 its retracted position thereby preventing it from 14 contacting the contact rod 82.

is However, during braking of the truck, such 16 as downhill braking or the like, the operator of the 17 truck (or the engine control module 60 itself) may 18 switch the engine 10 into its brake mode of operation 19 in order to assist the truck's main braking system in the slowing of the truck. When the engine 10 is 21 being operated in its brake mode of operation, the 22 engine control module 60 controls operation of the 23 actuator assemblies 66 of the compression release 24 brake assembly 64 such that the exhaust valves 42 are selectively opened in order to release compressed gas 26 within the engine cylinders. In particular, the 27 engine control module 60 generates an output pulse 28 which opens the solenoid-controlled hydraulic valve 29 74 of the actuator assembly 66 associated with the particular piston/engine cylinder. opening of the 31 solenoid-controlled hydraulic valve 74 allows 21 1 pressurized hydraulic fluid from the fluid manifold 2 48 to be advanced through the solenoid-controlled 3 hydraulic valve 74 and into the fluid chamber 70 of 4 the actuator assembly 66. The presence of pressurized hydraulic fluid in the fluid chamber 70 6 causes the piston 72 to be urged upwardly (as viewed 7 in FIG. 3) into an extended position in which the 8 contact side 80 of the piston 72 is urged into 9 contact with a portion of the exhaust rocker arm 20.

Moreover, when the engine 10 is operated in 11 its brake mode of operation, the fuel injection 12 assembly 44 is idled. In particular, during 13 operation of the engine 10 in its brake mode of 14 operation, the engine control module 60 does not open any of the solenoid-controlled hydraulic valves.58 16 associated with the fuel injectors 46 thereby 17 preventing fuel from being injected into the 18 corresponding engine cylinders.

19 During operation of a hydraulic compression brake, if a fluid pressure that is too low is applied 21 during brake actuation, the pressure may not create 22 enough force to enable the opening of the exhaust 23 valve 42. A fluid pressure too large may cause the 24 lift of exhaust valve 42 toovershoot and potentially contact the cylinder piston 72. In addition, an 26 excessive fluid pressure may cause an excessive 27 exhaust valve actuation speed, which may cause the 28 valve 42 to close with a strong return force, 29 potentially prematurely wearing down the components involved.

22 1 The present invention provides a method and 2 apparatus of controlling the actuation of a 3 compression brake associated with a combustion 4 engine. The engine includes a fluid circuit for delivering a fluid to the compression brake. The 6 method includes the steps of: establishing a desired 7 timing of the actuation of the brake, determining the 8 air pressure of the engine, determining the desired 9 fluid pressure in response to the timing and the air pressure; and controlling the compression brake in 11 response to the desired fluid pressure.

12 The application of pressurized fluid 13 against the piston 72 creates a force that is applied 14 to an engine cylinder's exhaust valve 42. The timing is of the actuation is done to open the cylinder's 16 exhaust valve 42 when the associated piston, or crank 17 angle, has achieved a desired position within the 18 piston cycle, e.g., the compression stroke. When 19 opened, the compressed air passes through the exhaust valve 42, thereby dissipating energy. The energy 21 loss results in a retarding torque on the crankshaft 22 that helps slow down the speed of the engine.

23 Achieving the desired opening of the exhaust valve 24 against the cylinder pressure varies, in part, on boost pressure and desired brake actuation timing, 26 e.g., piston position, or crank angle position.

27 Therefore, the present invention preferably 28 dynamically determines a desired brake actuation 29 time, and senses the air pressure, e.g., boost pressure, of the engine. A desired fluid pressure is 31 then determined in response to the desired timing and 23 1 the boost pressure. The compression brake is then 2 controlled in response to the desired fluid pressure, 3 thereby enabling the desired release of compressed 4 air through the exhaust valve.

Other aspects, objects, and advantages of the 6 present invention can be obtained from a study of the 7 drawings, the disclosure, and the claims.

24 1 Claims 2 3 1. A method of controlling an actuation of a 4 compression brake associated with a combustion engine, the engine including a fluid circuit for delivering a 6 fluid to the compression brake, the fluid enabling the 7 control of the compression brake, the engine including a 8 cylinder having an associated exhaust valve, comprising 9 the steps of:

establishing a desired timing of an actuation 11 of said brake; 12 determining an air pressure of said engine; 13 determining a desired fluid pressure in 14 response to said timing and said air pressure; and controlling said compression brake actuation in 16 response to said desired fluid pressure 17 18 2. A method, as set forth in claim 1, wherein 19 the step of establishing a desired brake actuation timing includes the step of dynamically determining said desired 21 brake actuation timing.

22 23 3. A method, as set forth in claim 1, wherein 24 said desired brake actuation timing is a predetermined value.

26 27 4. A method, as set forth in claim 1 or 2, 28 wherein the step of dynamically determining said desired 29 brake actuation timing further comprises the steps of:

31 determining a desired engine speed; 32 determining an actual engine speed; 1 determining a desired braking torque in response to 2 said desired and actual engine speeds; 3 determining a desired brake actuation timing in 4 response to said desired braking torque and said actual engine speed.

6 7 5. A method, as set forth in any of claims 1 8 to 4, wherein the step of determining an air pressure 9 includes the step of determining a boost pressure of said engine.

11 12 6. A method, as set forth in any of claims 1 13 to 5, wherein the step of determining a boost pressure 14 includes the step of sensing said boost pressure.

is 16 7. A method, as set forth in claim 5 or 6, 17 further comprising the step of determining a cylinder 18 pressure in response to said boost pressure and said 19 desired brake timing.

21 8. A method, as set forth in claim 7, wherein 22 the step of determining said cylinder pressure further 23 comprises the steps of:

24 correlating said desired brake timing with an engine speed; and 26 determining said cylinder pressure in response to 27 said boost pressure and said correlation.

28 29 9. A method, as set forth in claim 8, wherein said engine speed is an actual engine speed.

31 32 10. A method, as set forth in claim 8, wherein 33 said engine speed is indicative of an associated piston 26 1 position, and wherein said step of correlating said 2 desired brake timing with said engine speed includes the 3 step of correlating said desired brake timing with said 4 associated piston position.

6 11. A method, as set forth in any of claims 8 7 to 10, wherein the step of determining said desired fluid 8 pressure further comprises the step of determining said 9 desired fluid pressure in response to said cylinder pressure.

11 12 12. A method, as set forth in any of claims 1 13 to 11, wherein the step of controlling said brake 14 actuation includes the step of controlling an exhaust is valve actuation speed.

16 17 13. A method, as set forth in any of claims 1 18 to 11, wherein the step of controlling said brake 19 actuation includes the step of controlling an exhaust valve lift.

21 22 14. A method, as set forth in any of claims 1 23 to 4, wherein the step of determining said air pressure 24 includes the steps of:

sensing a signal indicative of an engine cylinder 26 pressure; and 27 determining a cylinder pressure in response to said 28 sensed cylinder pressure signal.

29 15. A method, as set forth in claim 14, 31 wherein the step of determining said desired fluid 32 pressure includes the step of determining said desired 33 fluid pressure in response to said cylinder pressure.

27 1 16. An apparatus adapted to control an 2 actuation of a compression brake associated with a 3 combustion engine, the engine including a fluid circuit 4 for delivering a fluid to the compression brake, the fluid enabling the control of the compression brake, the 6 engine including a cylinder having an associated exhaust 7 valve, comprising:

8 a speed sensor adapted to sense an engine 9 characteristic indicative of an engine speed and responsively generate a speed signal; 11 an air pressure sensor adapted to sense a 12 characteristic indicative of an engine air pressure and 13 responsively generate an air pressure signal; and 14 a controller adapted to receive said speed is signal and said air pressure signal, establish a desired 16 timing of an actuation of said brake, determine an air 17 pressure of said engine in response to said air pressure 18 signal, dynamically determine a desired fluid pressure in 19 response to said brake timing and said air pressure, and control said compression brake actuation in response to 21 said desired fluid pressure.

22 23 17. An apparatus, as set forth in claim 16, 24 wherein said controller is further adapted to establish said desired timing dynamically in response to said 26 actual engine speed and a desired engine speed.

27 28 18. An apparatus, as set forth in claim 16 or 29 17, wherein said air pressure sensor is a sensor adapted to sense a characteristic of an engine boost pressure.

31 32 19. An apparatus, as set forth in any of 33 claims 16 to 18, wherein said air pressure sensor is a 28 1 sensor adapted to sense a characteristic of an engine 2 cylinder pressure.

3 4 20. An apparatus, as set forth in any of claims 16 to 19, further comprising a fluid pressure 6 sensor, said fluid pressure sensor adapted to sense an 7 actual pressure of said fluid and responsively generate a 8 fluid pressure signal.

9 21. An apparatus, as set forth in claim 20, 11 wherein said controller is further adapted to receive 12 said fluid pressure signal, compare said actual fluid 13 pressure with said desired fluid pressure, and control 14 said brake actuation in response to said comparison.

is 16 22. An apparatus, as set forth in claim 20 or 17 21, further including a control valve adapted to receive 18 a fluid pressure command signal and control said actual 19 fluid pressure in response to said command signal, wherein said controller is further adapted to generate 21 said command signal in response to said comparison.

22 23 23. An apparatus, as set forth in claim 21, 24 further including a variable displacement pump adapted to receive a fluid pressure command signal and control said 26 actual fluid pressure in response to said command signal, 27 wherein said controller is further adapted to generate 28 said command signal in response to said comparison.

29 24. An apparatus, as set forth in claim 18 or 31 19, wherein said controller is further adapted to 32 determine a cylinder pressure in response to said boost 33 pressure and said desired timing.

29 1 25. An apparatus, as set forth in claim 19, 2 wherein said controller is further adapted to dynamically 3 determine said desired fluid pressure in response to said 4 cylinder pressure.

6 26. An apparatus, as set forth in any of 7 claims 19 to 25, further comprising a temperature sensor 8 adapted to sense a temperature of said fluid and generate 9 a temperature signal, wherein said controller is further adapted to receive said temperature signal and determine 11 said desired fluid pressure in response to said cylinder 12 pressure and said fluid temperature.

13 14 27. A method of controlling an actuation of a is compression brake substantially as hereinbefore described 16 and illustrated in the accompanying drawings.

17 18 28. An apparatus for controlling an actuation 19 of a compression brake substantially as hereinbefore described and illustrated in the accompanying drawings.